An apparatus of that kind is to be found for example in AT 407 538. That apparatus not only includes the float, the blocking element and a coupling linkage by way of which the float movement is converted into the closing movement of the blocking element, but also the outlet riser pipe with a horizontal discharge pipe. Fixed to the lower end of the outlet riser pipe are plates on which connecting bars are displaceably guided. Fixed in the upper region of the outlet riser pipe is an outer holding portion on which double-armed levers are mounted, the levers coupling the float to the connecting bars in such a way that the downwardly sinking float lifts the blocking element.
The apparatus is fitted as a complete unit into a separation vessel and includes an installation housing with an outlet riser pipe and the discharge pipe, and with at least one filter wall and a mounting plate which can be fixed in the separation vessel. In the event of troubles, either they have to be rectified in the installed condition in the separation vessel or the entire installation housing has to be removed. Both options are unsatisfactory and therefore the object of the invention is to improve the construction in such a way that it can be easily and simply fitted and broken down into its functional parts.